<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    const arr =  [
   { 'id': '29', 'pid': '',     'name': '总裁办' },
   { 'id': '2c', 'pid': '',     'name': '财务部' },
   { 'id': '2d', 'pid': '2c', 'name': '财务核算部'},
   { 'id': '2f', 'pid': '2c', 'name': '薪资管理部'},
   { 'id': 'd2', 'pid': '',     'name': '技术部'},
   { 'id': 'd3', 'pid': 'd2', 'name': 'Java研发部'}
 ]
 const mapObj = {}
 arr.forEach(item=>{
  console.log(item,'item');
  if(!item.children){
    item.children = []
  }
  mapObj[item.id]=item
 })
 console.log(mapObj,'mapObj');
 const newArr = []
 arr.forEach(item=>{
  const parent = mapObj[item.pid]
  if(parent){
    parent.children.push(item)
  }else{
    newArr.push(item)
  }
 })
 console.log(newArr,'newArr');
  </script>
</body>
</html>